Preparation method for silver nanowires with uniform aspect ratio

ABSTRACT

A preparation method for silver nanowires with a uniform aspect ratio, including: dissolving at a certain temperature silver nitrate in glycerol to get a solution A; dissolving at a certain temperature polyvinylpyrrolidone (PVP) in glycerol to get a solution B; mixing uniformly the solution A and the solution B to form a solution C; then, adding a certain amount of a medium into the solution C and mixing uniformly to form a solution D, finally, transferring the solution D into a reaction kettle, putting the reaction kettle into an oven with a set temperature, and ending the reaction after a certain time of reaction. The reactants are centrifuged twice to obtain precipitated silver nanowires.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a preparation method for silvernanowires, and more particularly, to a preparation method for silvernanowires with a uniform aspect ratio.

2. Description of Related Art

Based on the properties of high specific surface area, electricalconductivity and thermal conductivity, silver nanowires have a broadapplication prospect. Especially, the silver nanowires can be used as analternative material of ITO in fields such as solar energy, OLED, andflexible and large-size touch screen displays, and used in fields suchas conductive polymers, composite materials, and electrode printing inkadditives.

Therefore, the preparation of silver nanowires has become a focus ofresearchers. At present, there are many documents and patent reports onthe preparation methods and applications of silver nanowires. Forexample, Xia Younan, the first one who prepares silver nanowires with apolyol method, proposed the preparation of silver nanowires with a highaspect ratio by using Pt as seeds and reducing silver nitrate byethylene glycol (Advanced Materials (2002) 14,883).The polyol reductionmethod was combined with the hydrothermal method, and a small amount ofsodium chloride, ferric chloride, copper chloride and other metal halidewere introduced to function with Ag ions to form a colloid, which servesas seeds to prepare silver nanowires. The silver nanowires can bequickly prepared by the combination of the polyol method and themicrowave method. However, the silver nanowires thus obtained have arelatively non-uniform aspect ratio, and have a large amount ofimpurities. For example, Chinese Patent Application No. 200810019828.6disclosed a batch preparation method for silver nanowires, and ChinesePatent Application No. 201010559335.9 disclosed a method for preparingsilver nanowires with controlled diameter by using a cation-controlledmicrowave method. However, he prepared silver nanowires are less than 30μm in length, and have a non-uniform aspect ratio. Chinese Patent No. CN1843670A reported the use of a composite solvent of glycerol and wateror ethanol or isopropanol for reduction to prepare silver nanowires. Theobtained silver nanowires have a length of 5-200 μm and a diameter of70-90 nm. Although many preparation methods for silver nanowires havebeen reported, few of them can obtain silver nanowires with a uniformaspect ratio and no other particles or impurities. Therefore, it is veryimportant to invent a method that has a stable process, has fewercontrol factors, is simple and quick, can prepare a large quantity of Agnanowires.

SUMMARY OF THE INVENTION

The present invention is directed to a preparation method of silvernanowires with a uniform aspect ratio, which is simple, easy to control,and cost-effective.

The present invention is achieved through the following technicalsolution.

A preparation method for silver nanowires includes the following steps:

-   -   (1) dissolving silver nitrate in glycerol to get a solution A;    -   (2) dissolving polyvinylpyrrolidone in glycerol to get a        solution B;    -   (3) mixing uniformly the solution A and the solution B to form a        solution C; and    -   (4) adding an ultrapure water medium into the solution C and        mixing uniformly to form a solution D, finally, transferring the        solution D into a reaction kettle for reaction at 150° C±10° C.,        and centrifuging the reactants to obtain silver nanowires. The        obtained silver nanowires have high purity and a uniform aspect        ratio.

Preferably, reaction time in the reaction kettle is 9-10 hours.

To further improve purity and uniformity of the aspect ratio of thesilver nanowires, preferably, in step (1), 0.16 g-0.32 g silver nitrateis dissolved at room temperature in 20 ml of glycerol to get thesolution A.

More preferably, in step (2), 5 g-7 g polyvinylpyrrolidone is dissolvedat room temperature in 80 ml of glycerol to get the solution B.

More preferably, in step (4), 2.5 m1-10 ml of the ultrapure water isadded into the solution C and mixed uniformly to form the solution D.

Further, the centrifuging is performed twice.

The present invention has the following beneficial effects:

The preparation method of the present invention is simple to operate,easy to control, cost-effective, and very suitable for large-scaleindustrial production. The prepared silver nanowires have a uniformaspect ratio, and transparent conductive films based on the silvernanowires have a high transparency of 90-91%. The silver nanowires havea diameter of up to 30-40 nm and a length of 10-20 μm, and the silvernanowires with the aspect ratio have small resistance, which isbeneficial to the improvement of electrical conductivity. In addition,the silver nanowires have no particles and feature high purity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a scanning electron microscope (SEM) diagram of a silvernanowire synthesized in Example 1 of the present invention; and

FIG. 2 is a diagram showing transmittance of a conductive thin film madeof silver nanowires synthesized in Example 1 of the present invention.

DESCRIPTION OF THE EMBODIMENTS

The technology of the present invention will be further described belowwith reference to specific examples.

EXAMPLE 1

0.16 g silver nitrate was dissolved at room temperature in 20 ml ofglycerol to get a solution A; 5 g polyvinylpyrrolidone was dissolved atroom temperature in 80 ml of glycerol to get a solution B; the solutionA and the solution B were mixed uniformly to form a solution C; then, 5ml of ultrapure water was added into the solution C and mixed uniformlyto form a solution D, finally, the solution D was transferred into areaction kettle, the reaction kettle was put into an oven with a settemperature of 160° C., and the reaction ended after a certain time ofreaction.

The Ag nanowire mother solution in the reaction kettle was diluted withalcohol and centrifuged twice to obtain precipitated silver nanowireshaving a diameter of 30-40 nm and a length of 10-20 μm, which weredispersed in isopropanol. FIG. 1 is a scanning electron microscope (SEM)diagram of a silver nanowire synthesized in Example 1.

The silver nanowires prepared in Example 1 above were formulated into 1g/L silver nanowire slurry, and 500 μL of slurry was uniformly coated onan A4-size transparent film to prepare a transparent conductive film.The sheet resistance of the transparent conductive film was 42 ohm/sq.Then, the transmittance of the transparent conductive film was measuredwith a UV-Vis spectrophotometer. As shown in FIG. 2, at the visiblelight wavelength of 550 nm, the transmittance of the transparentconductive film was 90.8%.

Example 2

0.16 g silver nitrate was dissolved at room temperature in 20 ml ofglycerol to get a solution A; 5 g polyvinylpyrrolidone was dissolved atroom temperature in 80 ml of glycerol to get a solution B; the solutionA and the solution B were mixed uniformly to form a solution C; then,2.5 ml of ultrapure water was added into the solution C and mixeduniformly to form a solution D, finally, the solution D was transferredinto a reaction kettle, the reaction kettle was put into an oven with aset temperature of 160° C., and the reaction ended after a certain timeof reaction.

The Ag nanowire mother solution in the reaction kettle was diluted withalcohol and centrifuged twice to obtain precipitated silver nanowireshaving a diameter of 30-40 nm and a length of 10-20 which was dispersedin isopropanol.

Example 3

0.32 g silver nitrate was dissolved at room temperature in 20 ml ofglycerol to get a solution A; 7 g polyvinylpyrrolidone was dissolved atroom temperature in 80 ml of glycerol to get a solution B; the solutionA and the solution B were mixed uniformly to form a solution C; then, 10ml of ultrapure water was added into the solution C and mixed uniformlyto form a solution D, finally, the solution D was transferred into areaction kettle, the reaction kettle was put into an oven with a settemperature of 160° C., and the reaction ended after a certain time ofreaction.

The Ag nanowire mother solution in the reaction kettle was diluted withalcohol and centrifuged twice to obtain precipitated silver nanowireshaving a diameter of 30-40 nm and a length of 10-20 μm, which wasdispersed in isopropanol.

1. A preparation method for silver nanowires, comprising the followingsteps: (1) dissolving silver nitrate in glycerol to get a solution A;(2) dissolving polyvinylpyrrolidone in glycerol to get a solution B; (3)mixing uniformly the solution A and the solution B to form a solution C;and (4) adding an ultrapure water medium into the solution C and mixinguniformly to form a solution D, finally, transferring the solution Dinto a reaction kettle for reaction at 150° C.±10° C., and centrifugingthe reactants to obtain silver nanowires.
 2. The preparation methodaccording to claim 1, wherein reaction time in the reaction kettle is9-10 hours.
 3. The preparation method according to claim 1, wherein instep (1), 0.16 g-0.32 g silver nitrate is dissolved at room temperaturein 20 ml of glycerol to get the solution A.
 4. The preparation methodaccording to claim 3, wherein in step (2), 5 g-7 g polyvinylpyrrolidoneis dissolved at room temperature in 80 ml of glycerol to get thesolution B.
 5. The preparation method according to claim 4, wherein instep (4), 2.5 ml-10 ml of the ultrapure water is added into the solutionC and mixed uniformly to form the solution D.
 6. The preparation methodaccording to claim 1, wherein the centrifuging is performed twice. 7.The preparation method according to claim 5, wherein the centrifuging isperformed twice.
 8. The preparation method according to claim 2, whereinin step (1), 0.16 g-0.32 g silver nitrate is dissolved at roomtemperature in 20 ml of glycerol to get the solution A.
 9. Thepreparation method according to claim 8, wherein in step (2), 5 g-7 gpolyvinylpyrrolidone is dissolved at room temperature in 80 ml ofglycerol to get the solution B.
 10. The preparation method according toclaim 9, wherein in step (4), 2.5 ml-10 ml of the ultrapure water isadded into the solution C and mixed uniformly to form the solution D.11. The preparation method according to claim 10, wherein thecentrifuging is performed twice.
 12. The preparation method according toclaim 2, wherein the centrifuging is performed twice.